[Qemu-devel] Windows vioinput guest driver tablet input bug

[Justin Gatzen]

Hi,

The vioinput Windows guest driver does not seem to work with mouse wheel or
side buttons for virtio-tablet-pci devices, while virtio-mouse-pci works as
expected. Linux guest drivers are unaffected. Tablets are being categorized as
mice due to the EXPOSE_ABS_AXES_WITH_BUTTONS_AS_MOUSE compile flag. But when
there are no relative REL_X or REL_Y input axes the driver ignores all other
relative axis entries. Mouse wheel is one such relative axis. I've attached a
proof of concept fix for the guest driver that seems to fix both the mouse
wheel and side buttons but I believe this needs a more robust fix and deeper
look at the HIDMouseProbe function.

Thanks,
Justin


diff --git a/vioinput/sys/HidMouse.c b/vioinput/sys/HidMouse.c
index 69dac235..ea188991 100644
--- a/vioinput/sys/HidMouse.c
+++ b/vioinput/sys/HidMouse.c
@@ -325,7 +325,11 @@ HIDMouseProbe(
     DynamicArrayReserve(&AxisMap, AXIS_MAP_INITIAL_LENGTH * 2 * sizeof(ULONG));

     // Windows won't drive a mouse without at least the X and Y relative axes
-    if (InputCfgDataHasBit(pRelAxes, REL_X) &&
InputCfgDataHasBit(pRelAxes, REL_Y))
+    if (InputCfgDataHasBit(pRelAxes, REL_X) &&
InputCfgDataHasBit(pRelAxes, REL_Y)
+#ifdef EXPOSE_ABS_AXES_WITH_BUTTONS_AS_MOUSE
+        || (pMouseDesc->uNumOfButtons > 0 &&
InputCfgDataHasBit(pAbsAxes, ABS_X) && InputCfgDataHasBit(pAbsAxes,
ABS_Y))
+#endif // EXPOSE_ABS_AXES_WITH_BUTTONS_AS_MOUSE
+        )
     {
         for (i = 0; i < pRelAxes->size; i++)
         {
@@ -391,7 +395,7 @@ HIDMouseProbe(
     }

 #ifdef EXPOSE_ABS_AXES_WITH_BUTTONS_AS_MOUSE
-    if (uNumOfRelAxes == 0 &&
+    if ((!InputCfgDataHasBit(pRelAxes, REL_X) ||
!InputCfgDataHasBit(pRelAxes, REL_Y)) &&
         pMouseDesc->uNumOfButtons > 0 &&
         InputCfgDataHasBit(pAbsAxes, ABS_X) &&
InputCfgDataHasBit(pAbsAxes, ABS_Y))
     {